GB2474659A

GB2474659A - Internal combustion engine starter-generator drive system with two one-way clutches

Info

Publication number: GB2474659A
Application number: GB0918405A
Authority: GB
Inventors: Robert Wartanian
Original assignee: GM Global Technology Operations LLC
Current assignee: GM Global Technology Operations LLC
Priority date: 2009-10-20
Filing date: 2009-10-20
Publication date: 2011-04-27
Also published as: US20110121571A1; RU2010142897A; GB0918405D0; CN102042147A

Abstract

A torque transmitting mechanism 1 of an i.c. engine comprises a starter-generator 2, a crankshaft side member 3 which rotates in conjunction with a crankshaft 4, a first one-way clutch 5 arranged to transmit torque from the starter 6 to the crankshaft side member 3 and a second one-way clutch 7 arranged to transmit torque from the crankshaft side member 3 to the generator 8. The starter 6 is in constant engagement with the crankshaft side member 3. A combined starter-generator 2, fig.2, may have a gear drive 15 from the starter 6 and a belt drive 16 to the generator 8. The first one-way clutch 5 may be located between the ring gear 17 and the crankshaft 4 of the gear drive 15; once engine rpm is above a predetermined limit, the second one-way clutch 7 is actuated to couple the belt drive 16 to the crankshaft.

Description

A torque transmitting mechanism of an internal combustion en-gine, a vehicle and a method of transmitting torque The present application relates to a torque transmitting mechanism of an internal combustion engine, a vehicle compris- ing a torque transmitting mechanism and a method of transmit-ting torque in an internal combustion engine.

It is desirable to reduce fuel consumption as well as the emissions of internal combustion engines and, in particular, internal combustion engines of automotive vehicles. Various approaches may be used, either singly or together. For exam-ple, the fuel consumption may be reduced by more efficient fuel combustion and/or reducing the weight of the vehicle.

Consumption of fossil fuels such as petrol and diesel may be reduced by providing an additional energy source such as a battery in so-called hybrid-drive systems.

Techniques such as regenerative braking may also be used to regain energy which would otherwise be dissipated in the form of heat. This regained energy can be used to power either the vehicle or auxiliary systems within the vehicle.

Other approaches include stop and start systems in which the internal combustion engine is automatically switched off should the vehicle temporarily stop and the engine idle. The internal combustion engine is restarted when the driver wishes to move forward and operates the clutch. These methods are useful for improving fuel efficiency in heavy traffic situa-tions which may occur in towns and cities, particularly during the rush hour.

DE 10 2004 008 649 Al discloses a drive system for an internal combustion engine in which a starter-generator is coupled to the crankshaft by a belt. The starter is used to start the en-gine by driving the crankshaft and, during operation of the engine, the crankshaft drives the generator.

A free engine clutch is provided in this drive system between a drive wheel and a generator shaft that links the drive wheel to the generator shaft when the internal combustion engine drives the generator and releases this link if drive torque is low or equals zero. The free engine clutch is bypassed by an engaging and disengaging a clutch when the starter-generator starts up or cranks the internal combustion engine. However, further improvements are desirable to further improve fuel economy.

The present application provides a torque transmitting mecha-nism of an internal combustion engine that comprises a starter-generator, a crankshaft side member which rotates in conjunction with a crankshaft, a first one-way clutch arranged to transmit torque from the starter to the crankshaft side member and a second one-way clutch arranged to transmit torque from the crankshaft side member to the generator. The starter is in constant engagement with the crankshaft side member.

The torque transmitting mechanism enables torque to be trans-mitted between the starter-generator and the crankshaft. In particular, the first one-way clutch enables torque to be transmitted from the starter to the crankshaft side member, the crankshaft and the internal combustion engine. The second one-way clutch enables torque to be transmitted from the crankshaft side member to the generator and regain energy from the rotating crankshaft which is fed into the generator.

The starter-generator may be provided in the form of a com-bined starter-generator and may replace a starter-alternator system.

The starter is in constant engagement with the crankshaft side member. The torque transmitting mechanism can be used as part of a stop and start system that is quick efficient since the torque can be quickly transmitted from the starter to the crankshaft side member when the engine starts, since the starter is in constant engagement with the crankshaft side member.

Furthermore, the engine does not have to be stopped completely for the starter to drive the crankshaft side member since the starter is constantly engaged with the crankshaft side member.

Therefore, the torque transmitting mechanism according to the present application enables the fuel economy of the internal combustion engine to be further improved.

In an embodiment, the starter is configured to drive the crankshaft side member and to drive the crankshaft when the first one-way clutch is engaged and the crankshaft is config- ured to drive the generator upon engagement of the second one-way clutch. In particular, the first and second clutches are configured so that only one of the first and second clutches is engaged at any one time so that the two torque transmitting directions are decoupled from one another. Therefore, torque can either be transmitted either from the starter to the crankshaft side member or from the crankshaft to the genera-tor. This increases the efficiency of the system.

The starter-generator is coupled to the crankshaft by two in-dependent drives which are operated one at a time. The starter-generator may be coupled to the crankshaft side member using various drive mechanisms. The two drives may operate on the same principle or may be different. In an embodiment, the crankshaft side member is coupled to the starter by a gear drive and to the generator by a belt drive. The belt drive may be a V-Belt drive, a timing chain drive or a flat belt drive.

In an embodiment, the crankshaft side member comprises a first ring gear for coupling the crankshaft side member to the starter via a gear drive and a pulley for coupling the crank-shaft side member to the generator via a belt drive.

In one embodiment, the starter is coupled to the first ring gear by a pinion gear which is in constant mesh with the first ring gear so that the starter is in constant engagement with the crankshaft side member.

In a further embodiment, the generator is coupled to the crankshaft side member by a belt drive, a timing chain drive or a gear pair. A belt drive or timing chain drive may be used if the arrangement is situated in the air. A gear pair may be used if the arrangement is situated in oil.

In a further embodiment, whilst the starter drives the crank-shaft, the second clutch is disengaged so that the second drive, e.g. the belt drive, freewheels and torque is not transmitted from the crankshaft to the generator. The genera-tor is decoupled from the crankshaft.

In a further embodiment, whilst the crankshaft drives the gen-erator, the first clutch is disengaged so that the first drive, e.g. a gear drive, freewheels and the starter is de-coupled from the crankshaft side member so that torque is not transmitted from the starter to the crankshaft side member.

In an embodiment, the first one-way clutch is configured to be actuated at a predetermined rpm (revolutions per minute) of the crankshaft to decouple the starter from the crankshaft.

This configuration enables the starter to be coupled to the crankshaft so as to start the crankshaft rotating and start the internal combustion engine. Once a predetermined rpm of the crankshaft has been reached which is indicative that the engine is running, the first one-way clutch is actuated so as to decouple the starter from the crankshaft. This decoupling may occur automatically as a result of the design of the first one-way clutch.

In a further embodiment, the second one-way clutch is config- ured to be actuated above this predetermined rpm of the crank-shaft so as to couple the crankshaft to the generator so that the crankshaft can drive the generator once the internal com-bustion engine is running. Since the second one-way clutch is actuated above the predetermined rpm, the crankshaft is cou-pled to the generator only when the starter is decoupled from the crankshaft.

In a further embodiment, the one-way clutch transmits torque generated by the starter from the first ring gear to the crankshaft in one direction and prevents torque from being transmitted in the opposing direction. This enables the starter to be reliably coupled and decoupled from the crank-shaft.

The application also provides a vehicle comprising an internal combustion engine, such as diesel engine or spark ignition en-gine, which is coupled to a crankshaft and further comprises a torque transmitting mechanism according to one of the embodi-ments described above.

The application also provides a method of transmitting torque in an internal combustion engine between a starter-generator and a crankshaft which is coupled to the internal combustion engine. The starter is in constant engagement with a crank- shaft side member which rotates in conjunction with the crank-shaft. The method comprises engaging a first one-way clutch and transmitting torque from the starter to the crankshaft side member to drive the crankshaft side ntember and the crank-shaft. A second one-way clutch is engaged to transmit torque from the crankshaft side member to the generator in order to drive the generator. More particularly, at any one time, torque is transmitted either from the crankshaft side member to the generator or from the starter to the crankshaft side member. Torque is transmitted in only one direction at any one time.

If the rpm of the crankshaft is zero and the internal combus-tion engine the switched off, the first one-way clutch may be engaged to couple the starter to the crankshaft so that torque can be transmitted from the starter to the crankshaft and start the internal combustion engine.

The first one-way clutch may be disengaged at a predetermined rpm of the crankshaft so as to decouple the starter from the crankshaft. The predetermined rpm may be indicative that the internal combustion engine is running.

In a further embodiment, the second one-way clutch is engaged at a rpm above the predetermined rpm of the crankshaft so as to couple the crankshaft to the generator and transmit torque from the crankshaft to the generator as well as to the trans-mission of the vehicle. Therefore, the switchover in the torque direction, is dependent on the rpm of the crankshaft.

During engine starting, the first one-way clutch is engaged so that the crankshaft is driven by the starter. The starter's driving force is transferred to the engine crankshaft. Once the engine is running, the first one-way clutch freewheels and the engine's driving force is transferred to the transmission.

The second one-way clutch may be engaged so as to engage the generator with the crankshaft so that, additionally, the crankshaft drives the generator.

The mechanism which couples the starter to the crankshaft and the mechanism which couples the generator with the crankshaft are decoupled. Therefore, the torque transmitting mechanism includes two drives which are decoupled from one another and operated independently and generally alternately.

The starter-generator may replace a starter motor and alterna- tor so as to reduce weight and further improve fuel effi-ciency.

Embodiment will now be described with reference to be accompa-flying drawings.

Figure la illustrates a schematic diagram of a torque transmitting mechanism of an internal combus- tion engine operated according to a first em-bodiment, Figure lb illustrates a schematic diagram of a torque transmitting mechanism of the internal combus- tion engine operated according to a second em-bodiment, Figure 2 illustrates a perspective view of the torque transmitting mechanism of an internal combus-tion engine according to a third embodiment, Figure 3 illustrates a side view of the torque transmit-ting mechanism of figure 2,, and Figure 4 illustrates a second perspective view of the torque transmitting mechanism of figure 2.

A torque transmitting mechanism 1 of a non-illustrated inter- nal combustion engine of a vehicle is illustrated schemati-cally in figures la and lb. In particular, figures la and lb illustrate two different torque transmitting paths of the torque transmitting mechanism 1.

The torque transmitting mechanism 1 comprises a starter-generator 2 and a crankshaft side member 3 which rotates in conjunction with a crankshaft 4 which is coupled to the inter- nal combustion engine. The starter-generator 2 may be a com-bined starter-generator unit.

The torque transmitting mechanism 1 comprises a first one-way clutch 5 arranged to transmit to torque from the starter motor 6 of the starter-generator 2 to the crankshaft side member 3 and prevent torque from being transmitted in the opposing di-rection from the side crankshaft member 3 to the starter motor 6.

The torque transmitting mechanism 1 also includes a second one-way clutch 7 arranged to transmit torque from the crank- shaft side member 3 to the generator 8 of the starter-generator 2 and prevent torque from being transmitted in the opposing direction from the generator 8 to the crankshaft side member 3. The starter motor 6 is in constant engagement with the crankshaft side member 3.

Although the starter motor 6 is in constant engagement with the crankshaft side member 3, the first one-way clutch 5 cou-ples and decouples the starter motor 6 from the crankshaft side member so that torque is either transmitted to the crank-shaft side member 3 or is not transmitted to the crankshaft side member 3, respectively. However, since the starter motor 6 is in constant engagement with the crankshaft side member 3, the torque can be quickly and efficiently transferred from the starter motor 6 to the crankshaft side member 3 to start the internal combustion engine. This is useful in stop and start operation in which the internal combustion engine is automati- cally switched off when the engine idles and automatically re-started when the driver wishes to pull off.

Figure la illustrates a first operating mode of the torque transmitting mechanism 1 in which the starter motor 6 trans- mits torque to the crankshaft side member 3, indicated by ar-rows 9, which is transmitted to the crankshaft 4, indicated by arrow 10, in order to rotate the crankshaft 4 as indicated by arrow 11. This operating mode may be used to start the inter-nal combustion engine. In this embodiment, the first one-way clutch 5 is actuated so as to transmit torque from the starter motor 6 to the crankshaft side member 3 and crankshaft 4.

Figure lb illustrates a second operating mode of the torque transmitting mechanism 1 in which the first one-way clutch 5 is actuated so as to decouple the starter motor 6 from the crankshaft side member 3 and crankshaft 4 and in which the second one-way clutch 7 is actuated so as to couple the crank-shaft side member 3 to the generator B. In this second operating mode, the internal combustion engine is running and the crankshaft 4 is rotating and is driven by the internal combustion engine as indicated by arrow 12. The torque is transmitted from the crankshaft 4 and crankshaft side member 3 which rotates conjunction with the crankshaft 4 to the generator 6 as indicated by the arrows 13. In this em-bodiment, the starter motor 6 is still in constant engagement with the crankshaft side member 3 but decoupled from the crankshaft side member 3 so that torque is not transferred to or from the starter motor 6. In this embodiment, torque from the internal combustion engine is transmitted via the crank-shaft 4 to the transmission of the vehicle as illustrated by the arrow 14.

Figures 2 to 4 illustrate different perspective views of a torque transmission system 1' according to a third embodiment.

In all of the figures, the same reference numeral is used to indicate similar or identical parts.

The torque transmitting mechanism 1' according to the second embodiment comprises a combined starter-generator 2 which is coupled to a crankshaft side member 3 which rotates in con- junction with a crankshaft 4. The coupling rods 20 which cou-pie the crankshaft 4 to the internal combustion engine and translate in the reciprocating motion of the pistons within cylinders of the internal combustion engine to rotational movement of the crankshaft are also illustrated in figures 2 to 4.

The starter-generator 2 includes a gear drive 15 and a belt drive 16 which are decoupled from one another and which are driven independently of one another. The crankshaft side mem- ber 3 includes a first ring gear 17 which is coupled to a pin- ion gear 19 of the gear drive 15 which couples the starter-generator 2 and, in particular, the starter motor 6 of the combined starter-generator 2, to the crankshaft 4. The pinion gear 19 is in constant mesh with the first ring gear 17.

The crankshaft side member 3 also comprises a pulley 18 which couples the crankshaft 4 to a pulley 22 on the starter-generator 2 by belt 21 to form a belt drive 16. In particular, the belt drive 16 couples the crankshaft 4 to the generator 8 of the starter-generator 2.

The pulley 22 is arranged concentrically around the shaft axis of pinion gear 19 so that the pinion gear 19 protrudes from a central through-hole arranged in the pulley 22. The pinion gear 19 and pulley 22 are arranged separately from one another so that each can be driven independently of the other.

The first one-way clutch 5 is positioned between the first ring gear 17 and the crankshaft 4 and is configured to couple the first gear drive 15 to the crankshaft 4 so as to transmit torque from the starter motor 6 to the crankshaft 4 and thus start the engine. The first one-way clutch 5 and gear drive 15 may be of the type disclosed in WO 2007/148228 which is hereby incorporated by reference in its entirety.

The starter motor 6 is driven by a non-illustrated 12 volt power supply. Whilst the starter motor 6 transmits torque to the crankshaft 4 by means of the gear drive 15, the belt drive 16 freewheels. As the starter motor 6 drives the crankshaft 4, the rpm of the crankshaft and internal combustion engine in-creases and at a predetermined rpm, the external power supply is disconnected from the starter motor 6 and the gear drive 15 is decoupled from the crankshaft 4 so that the gear drive 15 freewheels.

Once the rpm of the engine is above this predetermined limit, the second one-way clutch 7 is actuated so as to couple the belt drive 16 to the crankshaft 4 by means of the pulleys 18, 22 and belt 21 so that torque is transmitted from the crank-shaft 4 to the generator 8. In this embodiment, the second one-way clutch 7 is positioned within the housing of the starter-generator 2. Whilst the generator 8 is coupled to the crankshaft 4 by the belt drive 16, the gear drive 15 free-wheels. The generator generates electricity which may be stored in the battery of the vehicle or used directly to power the vehicle or auxiliary systems of the vehicle.